Grooved valve stem guide

ABSTRACT

A guide for the stem of an intake or exhaust valve of an internal combustion engine which is provided with two grooves produced by a threading tap with one groove being deeper than the other. The function of the deeper groove is to supply oil to the sliding or bearing surfaces of the stem and guide and the shallower groove serves to retain the oil in the vicinity where it is most needed and thus enable the use of close clearances because of good lubrication. Clearance is provided between an engine valve stem and its guide to insure lubricant supply and to insure reduced wear when the stem is subjected to operating temperatures. Rapid wear occurs in conventional guides if the clearance is either too large or small and, furthermore, if it is too large excessive blowby and carbon buildup occur with excessive oil being lost through the guide.

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Attorney-Fryer, Tjensvold, Feix, Phillips & Lempio Peoria, lll.

1,599,172 9/1926 Goodbrake................... 308/5(V) through the guide.

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INVENTORS loi-IN c. ABRAHAM ALEXANDER. eoLoFF BY n 'M/W-h ATTORNEYS GROOVED VALVE STEM GUIDE According to the present invention, two grooves following parallel paths in the wall of the valve stem guide are provided and the grooves are of different depth and capacity for the performance of different functions. As more particularly contemplated by the present invention, the function of the shallower groove is to provide the incline planes needed to build up an oil film while the deeper groove is to supply oil to the sliding or bearing surfaces of the guide. A better understanding of the invention will be gained by reading the following specification wherein it is described in greater detail and with reference to the accompanying drawings.

In the drawings:

FIG. l is a fragmentary view of a part of an engine head and blocked with a passage leading from the combustion chamber of a cylinder (not shown), a valve closing the passage and a valve stem guide embodying the present invention.

FIG. 2 is an enlarged fragmentary view showing a portion of the valve stem and a portion of the guide and illustrating the configuration of grooves made in accordance with the present invention.

FIGS. 3 and.4 are views in elevation and partially in section of two types of taps which may be employed for cutting the grooves of the present invention in the valve stem guide.

In FIG. l of the drawings a portion of the head of an internal combustion engine is shown at as having a passage l2 closed by a valve I4. The passage l2 may be an intake passage for air or a fuel-air or other combustible mixture to be ignited in the engine combustion chamber which underlies the valve 14, or it may be a passage for exhaust gas emitted from the combustion chamber. While it is true that the exhaust valve is subjected to higher temperatures and generally more strenuous service, the invention is capable of use with either intake or exhaust valves.

The valve 14 is shown as having a stem 16 reciprocably mounted in a valve stem guide 18 which is fitted in a suitable bore in the cylinder head. The valve is generally spring closed and opened by a cam action in a conventional and well-known manner. Lubricant between the stem and the guide is also conventionally provided from above and f'lows down the stem to enter the upper end of the guide. Various types of grooves have been provided to feed lubricant throughout the length of the guide and insure its presence between the bearing or sliding surfaces of the stem and guide. One method of forming a groove has been with the use of a tap or tool, similar to a tap such as is used in cutting a female thread in a bore into which a male thread is to be fitted. Generally, the thread or groove follows a spiral path and each tum is sufficiently spaced from the next to provide lands or bearing areas between the turns.

In accordance with the present invention, two grooves are cut to form parallel spiral paths on the inner wall of the valve guide. Such grooves are shown generally at 20 in FIG. l and are enlarged in FIG. 2 where they appear as alternate triangular cross section grooves 22 and smaller truncated triangular cross section grooves 24. The larger grooves 22 serve, as explained above, to provide a passage for the relatively free flow of oil throughout the length of the stem guide. The smaller grooves are provided to insure that an oil film is formed and maintained throughout the length of the guide and that portion of the valve stem which slides within it. This oil film is built up because of the reciprocating motion of the valve stem. It appears if the small grooves are properly sized, the lower one or two turns of them become clogged or closed with carbon, resulting from the presence of hot exhaust gases, and this acts as a dam which prevents the downward flow of oil from these small grooves beyond the lower end of the valve guide. This carbon buildup also tends to prevent the loss of oil by not allowing the oil to drip from the lower end because of capillary action of the oil.

Two types of taps with which the groove pattern of FIGS. 1 and 2 can be successfully cut are shown in FIGS. 3 and 4. The tap of FIG. 3 is known as a tandem tap wherein the lower portion or that portion first entering the bore to be tapped is provided with one type of tooth, in this case, teeth 24a of truncated form for cutting the grooves 24 of FIG. 2. Following this portion of the tap and generally separated therefrom as by a groove 26 is a portion having teeth of triangular cross section as illustrated at 22a for cutting grooves like those illustrated at 22 in FIG. 2. The form of tap illustrated in FIG. 4 sometimes referred to as a double-start or double-thread tap has two sets of cutter teeth which are arranged to cut parallel spiral grooves at the same time, one set comprising teeth 24b, the other comprising teeth 22h so that teeth such as shown at 24 and 22 in FIG. 2 are formed simultaneously as the tap advances through the bore.

As distinguished from the double-tap grooving of the guides of the present invention, single taps have been employed but with the single groove the clearances are greater. For example, clearances of 0.002 to 0.003 inch have been conventional.

As distinguished from the relatively large clearances necessary with a single groove, the present invention allows much closer fits with a minimum of 0.0002 inch or even less and lubrication and wear characteristics are improved.

We claim:

l. A valve stem guide for use in a combustion engine, having two parallel spiral grooves cut along its inner cylindrical surface, the grooves being spaced apart and completely disposed radially outwardly of the cylindrical surface to form bearing surfaces therebetween with the bearing surfaces being of constant diametrical dimension along the inner cylindrical surface, one groove being larger and deeper than the other groove to provide adequate oil supply throughout the length of the guide, the other groove functioning to maintain an oil film upon the bearing surfaces.

2. The valve stem guide of claim l in which the deeper groove is of triangular cross section and the other groove is of truncated triangular cross section.

3. The valve stem guide of claim l in which the other groove is selectively sized so that its lower end tends to be closed by carbon deposition from hot exhaust gases, the closure restricting the downward flow of oil from the other groove. 

1. A valve stem guide for use in a combustion engine, having two parallel spiral grooves cut along its inner cylindrical surface, the grooves being spaced apart and completely disposed radially outwardly of the cylindrical surface to form bearing surfaces therebetween with the bearing surfaces being of constant diametrical dimension along the inner cylindrical surface, one groove being larger and deeper than the other groove to provide adequate oil supply throughout the length of the guide, the other groove functioning to maintain an oil film upon the bearing surfaces.
 2. The valve stem guide of claim 1 in which the deeper groove is of triangular cross section and the other groove is of truncated triangular cross section.
 3. The valve stem guide of claim 1 in which the other groove is selectively sized so that its lower end tends to be closed by carbon deposition from hot exhaust gases, the closure restrictiNg the downward flow of oil from the other groove. 